But lately, she’s been breezing by the cash register at her neighborhood Ralphs even with the usual crowds at the store.

“In the last month, I have noticed it was faster,” said Ricketts, 27, an actress from Los Angeles. “I thought I was dreaming.”

She wasn’t. To shave precious minutes off wait times, Ralphs has been installing technology to measure foot traffic in nearly all of its supermarkets.

Known as QueVision, the system uses hidden infrared cameras with body heat trackers to figure out how many customers are shopping at any given time. Managers use that information to redeploy workers to the cash registers when things get busy.

It’s already paying off. QueVision has trimmed the average time it takes to get to the front of the line to roughly 30 seconds from the national average of four minutes, a Ralphs spokeswoman said.

The checkout system is part of an effort by traditional grocery chains to evolve and stay competitive through the use of technology.

The $518 billion grocery store industry hasn’t made a transformational leap forward since the bar code scanner was introduced in the 1970s. Thin profit margins have kept the shopping experience pretty much the same for decades: squeaky shopping carts, long checkout lines and aggravating scavenger hunts to find products.

“You have an industry that’s been kind of stuck in time,” said Scott Mushkin, a grocery retail analyst at Wolfe Research. “Grocers have to invest. Their business models have been under so much pressure, they’re fighting for their lives.”

Tech takes root

Technologies that recently have made their way into supermarkets include digital signs that update prices and locations of products and offer promotions by time of day, such as coffee and granola bar specials for morning commuters.

To speed up the checkout process, customers can pay via fingerprint scanners or use smartphone applications to scan bar codes themselves. A self-propelled “smart” shopping cart that can follow customers and lead them to items is being tested.

Grocery chains are finally spending the time and money to modernize because they are nervous about losing out to rivals. Big-box retailers such as Target are beefing up their grocery sections, and Amazon.com has been aggressively rolling out its Amazon Fresh same-day grocery delivery service.

Grocery industry revenue shrank an average of 0.4 percent in each of the past five years, according to research firm IBISWorld. Companies were hit hard by the recession as high unemployment and low disposable income forced consumers to cut back on premium products and rely instead on cheaper generic brands and discounts.

Generation gap

Grocery stores especially want to appeal to younger shoppers, many of whom tend to avoid traditional supermarkets because they consider them as the place their parents shop. One way to woo smartphone-toting millennials is to make grocery shopping more tech-friendly, analysts said.

Midwest supermarket chain Hy-Vee and AT&T, for instance, teamed up to launch a mobile app with a voice-activated product locator.

Last year, Whole Foods loaned one of its shopping carts to Austin, Texas, tech firm Chaotic Moon, which used it to develop the SmarterCart, a grocery cart equipped with a tablet and Microsoft’s Kinect device.

Users can transfer their shopping list and dietary restrictions and preferences from a smartphone to the cart. When a user places an item into the SmarterCart that conflicts with their diet — say, a box of pasta that isn’t gluten-free — the self-propelled cart sends an alert and can lead the shopper to alternatives.